: Complexes of general formula [ Ru(bpy) 2 (L) ]CF 3 SO 3 , where bpy = 2,2′ - bipyridine, and L = Schiff bases derived from salicylaldehyde and amino acids (glycine ( 1a), cysteine (1b), methionine (1c ) and phenylalanine ( 1d )) were synthesized. Characterization based on elemental analysis, Ru content, mass, infrared and electronic spectra confirmed RuN 5 O coordination unlike 1b where coordination occurred via azomethine nitrogen and cysteine sulfur. Cyclic voltammograms, except 1b, showed several quasi- reversible redox pairs in the positive potential range, the first located at about 0.5 V, corresponding to similar heteroleptic Ru(II) bipyridyl complexes. Biological activity was tested by interactions with DNA and BSA. DNA binding constants of order 10 3 M − 1 , suggest groove binding due to bpy ligand and hydrogen bonding of the OH and CO groups from the imine moiety. In vitro BSA protein inhibition assay performed by spectrofluorimetry showed Complex : BSA binding in 1 : 1 ratio with K b of 10 4 M − 1 order. Cytotoxicity studies by MTT assay for 72 h of drug action revealed activity of 1a and 1d against breast cancer MCF- 7 cells with IC 50 values 32 ± 8 and 26 ± 1µM, respectively.

Spectrophotometric determination of ruthenium using 1,10-phenanthroline was modified and used for quantification of the ruthenium content in complexes. Complexes were decomposed by using aqua regia and a full recovery of ruthenium from thus obtained solutions was observed at pH 6 after three hours of heating at 90 °C with a hundredfold excess of phenanthroline. The modified procedure has several important advantages compared to the originally reported procedure. It is faster and more accessible for laboratory practice since it does not require tedious RuO4 distillation. Also it has much wider linearity range (20 μg L−1 to 12 mg L−1 compared to 162 μg L−1 to 1.62 mg L−1) and lower limit of quantification (30.4 μg L−1 compared to 100 μg L−1). Moreover, recoveries of ruthenium are practically quantitative and the single standard addition method, instead of the calibration curve method, can be successfully used for accurate analysis.

Four new heteroleptic copper(II) complexes having chalcone or flavonol ligands and Schiff base (N-phenyl-5-chlorosalicylideneimine) as co-ligand were prepared, chemically and structurally characterized and investigated as functional biomimetic catecholase models. The complexes were prepared by the solution synthesis and crystal and molecular structures were determined by X-ray diffraction. Complexes were chemically characterized by elemental analysis, infrared and electronic absorption spectroscopy as well as by electrochemical measurements. Copper(II) chalcone complexes, with square-pyramidal CuO4N core, are binuclear, featuring phenolate oxygen from the Schiff base as a bridging atom, while copper(II) flavonol complexes are mononuclear, and reveal a square planar CuO3N coordination core. Catalytic activity of the complexes in 3, 5-di-tert-butylcatechol oxidation was confirmed by spectrophotometric and electrochemical measurements. Kinetic measurements revealed that the binuclear (chalcone-containing) complexes have enhanced catalytic activity as compared to the mononuclear Cu(II) flavonol complexes. Relatively high kcat values (300 – 750 h–1) confirmed their respectable biomimetic catecholase-like activity.

Introduction: Treatment of cancer has been subject of great interest. Researchers are continuously searching for new medicines. In this sense, ruthenium complexes have big potential. Some evidences suggest that ruthenium compounds possess anticancer activities. We synthesized two recently published ruthenium(III) complexes with bidentate O,N and tridentate O,O,N Schiff bases derived from 5-substituted salicylaldehyde and aminophenol or anilineare. These compounds showed affinity for binding to the DNA molecule, however, insufficient data are available regarding their possible toxic effects on biological systems.Methods: In the present study we evaluated genotoxic, cytotoxic, and cytostatic effects of Na[RuCl2(L1)2] and Na[Ru(L2)2], using the Allium cepa assay.Results: Different toxic effects were observed depending on the substance, tested concentration, and endpoint measured. In general, the tested compounds significantly lowered the root growth and mitotic index values as compared to the control group. Additionally, a wide range of abnormal mitotic stages, both clastogenic and non-clastogenic were observed in the treated cells. Na[RuCl2(L1)2] significantly increased the frequency of sticky metaphases, chromosome bridges, micronuclei, impaired chromosome segregation, as well as number of apoptotic and necrotic cells over the controls. In contrast, Na[Ru(L2)2] did not show significant evidence of genotoxicity with regard to chromosome aberrations and micronuclei, however, significant differences were detected in the number of apoptotic and necrotic cells when the highest concentration was applied.Conclusions: In this study we demonstrated antiproliferative effects of Na[RuCl2(L1)2] and Na[Ru(L2)2]. At clinical level, these results could be interesting for further studies on anticancer potential of the ruthenium(III) complexes using animal models.

A dinuclear Schiff base RuII complex derived from 5-chlorosalicylaldehyde and 2-aminopyridine was synthesized. The structure of the compound was analyzed by mass spectrometry as well as IR, UV/Vis, and 1H NMR spectroscopy, along with chemical analysis,as well as magnetic, cyclovoltammetric and conductivity measurements. Two RuII atoms are octahedrally coordinated by azomethine and pyridine nitrogen atoms from two tridentate monobasic Schiff bases and bridging phenol oxygen atoms. The formula of the complex is [Ru2L2Cl2(Et2NH)(H2O)] [L = N-(2-pyridyl)-5-chlorosalicylideneimine and Et2NH = isodiethylamine]. The RuII atoms in the dinuclear neutral complex species have different coordination environments, RuN3O2Cl and RuN2O3Cl. Interaction with CT DNA showed moderate hydrophobic binding. The compound demonstrates strong activity against methicillin-resistant Staphylococcus aureus, methicillin-sensitive Staphylococcus aureus, and especially Enterococcus faecalis. Microbiological tests showed significant inhibition of growth and ability to kill pathogens, similar or even improved compared to reference antibiotics vancomycin.

The interaction of CT DNA by two anionic Ru(III) complexes with N-substituted salicylidenimine ligands was investigated by spectroscopic titration and cyclic voltammetry. The result gives a surprising evidence for intercalation of DNA by the negatively charged complex species containing non typical intercalating ligands with Kb of order 10 M. Na[RuCl2(N-R-5-X-salim)2], where R represents butyl or phenyl and X = H, Cl, were characterized on the basis of elemental analysis, MALDI-TOF mass spectrometry, infrared, UV / visible spectroscopic measurements and cyclic voltammetry. (doi: 10.5562/cca2216)